1. Field of the Invention
The present invention relates to a printing apparatus provided with a function of printing a copy number on a printout, a printing method therefor, and a program for implementing the printing method.
2. Description of the Related Art
Conventionally, in an image forming apparatus that prints highly confidential documents, it is a general practice to improve security by using an information leakage prevention function provided in the image forming apparatus. For example, an image forming apparatus has been proposed which is provided with the information leakage prevention function so that highly confidential document data stored in the apparatus may not be improperly printed (see Japanese Laid-Open Patent Publication (Kokai) No. 2006-005442, for example). However, in addition to preventing the confidential documents from being improperly printed, security for printout after being outputted has increased in importance.
For example, in an office or the like, there is often the case where the highly confidential document is outputted as the printout by using a printing apparatus and the printout are distributed to participants in a conference or the like. In such a case, the printed documents are generally collected after the conference or the like is finished, in order to prevent information leakage. The printing apparatus used in this case includes a printing apparatus provided with “copy number printing function” for printing a serial number as a watermark on the document to be outputted in units of number of copies. Typically, a copy number showing what number of copies the printout is, is used as this serial number (see Japanese Laid-Open Patent Publication (Kokai) No. 2005-305671, for example).
With this copy number printing function, it is unnecessary for a distributor of the printout to previously record the number of printed copies, the number of distributed copies and the like in a memo or the like before printing and distributing the documents. Moreover, when the printout are collected, the distributor can easily check whether or not there is leakage in the collection only by checking the serial number printed on the collected printout. Therefore, it is unnecessary to perform a task of checking the number of collected copies, comparing it with the numbers of printed and distributed copies, and checking whether or not the printout have been certainly collected. Furthermore, previously understanding a relationship between the printed copy number and the distributor enables to trace a source of leakage when the printout is leaked to the outside. In this way, the above described copy number printing function has been an important function recently in a printing market in which security is regarded as important.
However, although the copy number printing function in the above described conventional printing apparatus is a function which is effective in security, this function has a problem of a troublesome task in performing an additional printing while retaining the copy number to be printed, which imposes a significant burden on an operator.
For example, it is assumed that the operator has set the copy number printing function as enabled and has printed 10 copies of the confidential document, and as a result, has obtained the printout with the copy numbers from “1” to “10” printed thereon. Afterward, when the additional printing is performed, the operator has to set a starting number of the copy number to “11”, which comes after “10”, to execute the printing. However, at this point, the same copy number may be printed on the same document due to a mistake in the setting of the copy number and the like. If the same copy number has been printed, the collection of the documents cannot be easily checked, and in addition to that, the source of leakage cannot be traced when the printout is leaked to the outside, which becomes a significant drawback in terms of security. To prevent such a situation, the operator has to constantly operate in consideration of the copy number to be printed.
In addition, if the document is shared among multiple users, all users sharing the document have to consider the current copy number of the document, which makes management of the copy number further cumbersome and imposes a significant burden on the operator.